Brandon Lee was killed by a gun containing blanks - always treat a gun like its loaded.
I see a lot of posts pointing out the gun should have been checked for Baldwin. Doesn't really matter. This is the rule on and off movie sets.
Don't point the gun at another person on set, even if its supposed to contain blanks, and if a shot absolutely requires it they're supposed to use protection. Shielding for camera operators, for example. I tend to think Baldwin should have known better, considering the number of movies he's done.
Obviously they were cutting a lot of corners when it came to gun safety. Baldwin was a producer on the movie and had a say in that, possibly, so I'm not sure he's inncoent there either.